The invention relates to a source according to the preamble of claim 1 for installing a source into a gas deposition reactor. Particularly, the invention relates to a source for gas deposition methods, which source is insertable at least partly inside a source fitting provided in a gas deposition reactor or a source space connected to the source fitting, to an arrangement for installing a source into a gas deposition reactor, the arrangement comprising at least one source fitting for the source such that the source fitting is connected to a reaction space of the gas deposition reactor, and a source installable at least partly inside the source fitting or a source space connected to the source fitting, and to a method for installing a source into a gas deposition reactor and for removing the same therefrom.
When structures are manufactured by employing gas deposition methods, such as ALD (Atomic Layer Deposition) and other CVD (Chemical Vapor Deposition) methods, source materials are to be brought into a gaseous state prior to feeding them into a reactor space of a reactor. Many processes are provided with no suitable source materials in liquid or gaseous state, so such processes have to utilize solid materials. Since vapour pressures of solid materials are quite low (typically less than 1 mbar at room temperature), they have to be heated in order to achieve a sufficient vapour pressure. Solid sources have thus been developed.
In prior art, solid sources have been tubes that have been placed in an oven and provided with a source crucible therein. In such a solution, a source pipework of a reactor consists of a multi-branch, candelabrum-like pipework, which is preferably made of glass and in which different solid sources reside in different branches that can be heated independently, a reactor space of the reactor being provided at the foot of the candelabrum-like pipework. The process of charging the solid sources is carried out by inserting an open source crucible into a source tube by means of e.g. a thermo-element. In another embodiment, a source crucible was placed in a plastic bag while inserting it into a source tube so as to prevent the source material from becoming oxidized or from reacting with another substance present in room air or, in turn, from evaporating into room air.
A problem with the above-described arrangement is that installing a solid source material into a gas deposition reactor is not an inert procedure, but the arrangement is subject to contamination occurring in connection with installation and removal of the solid source, since the solid source materials used may be highly reactive and sensitive to oxygen and moisture, and they may emit detrimental compounds as vapour. In addition, this prior art solution for installing and removing a solid source is complex, unreliable and difficult to use.
Another prior art solution for installing a solid source into a gas deposition reactor is to utilize a metallic bottle equipped with valves such that a solid source is inserted in the metallic bottle, which, together with the valves, is placed in a vacuum or convection oven. This solution provides an inert method for installing a solid source, but the highest possible operating temperature, approximately 200 to 250° C., is determined by the valves, whose operating life becomes significantly shorter at high temperatures. If the valves are placed outside the oven, additional fittings have to be provided; furthermore, the structure develops heat bridges. In addition, the bottles and parts of the pipework are made of metal, which, due to possible chemical reactions, restricts possible solid source materials available. Furthermore, such bottles, being large and heavy, are difficult to install and detach, and such work also requires tools; in addition, the bottles are expensive. When being replaced, the pipeworks have to be flushed, which makes the solution even more complex.